Why some neural network models in the 1980s shown as circuit models
In the early days of neural networks the theorists and practitioners were educated in mathematics, psychology, neurophysiology, electrical engineering, and neurobiology. Computer science was still in its infancy. The first neural networks were modeled as electrical circuits.
There is evidence of this in the 1943 paper by Warren McCulloch and Walter Pitts [1], and a 1956 paper by Rochester et al. [2].
The latter paper uses terms such as 'circuits' and 'switching'.  One idea in the paper is explained in terms of a &quot;Eccles-Jordan Flip Flop circuit&quot; although there are no drawings.  Nathanial Rochester had designed the IBM 701k [3] and &quot;led the first effort to simulate a neural network&quot; [4]
Brain structure was discussed in terms of 'neural circuits' as early as 1937 [5].
I am not sure when the first electrical circuit diagram appeared in publication, but it makes sense that early neural network designers, would have thought of their implementation as such.
References:

[1] McCulloch, W. S., and Walter Pitts, W. (1943) A Logical Calculus of the Ideas Immanent in Nervous Activity. https://jontalle.web.engr.illinois.edu/uploads/498-NS.21/McCulloch-Pitts-1943-neural-networks-ocr.pdf
[2] Rochester, N., Holland, J., Haibt, L., &amp; Duda, W. (1956). Tests on a cell assembly theory of the action of the brain, using a large digital computer. IRE Transactions on Information Theory, Information Theory, IRE Transactions on, IRE Trans. Inf. Theory, 2(3), 80–93. https://doi-org/10.1109/TIT.1956.1056810
[3] Brief History of Neural Networks
https://www.linkedin.com/pulse/data-science-term-neural-networks-70-year-old-anchit-sharma/?trk=public_profile_article_view
[4] This Data Science term - Neural Networks is 70-Year-Old Technology!
https://medium.com/analytics-vidhya/brief-history-of-neural-networks-44c2bf72eec:
[5] Papez circuit, https://en.wikipedia.org/wiki/Papez_circuit